Planarization methods for patterned media disks

ABSTRACT

A method is provided for forming a plurality of regions of magnetic material in a substrate having a first approximately planar surface. The method comprises the steps of fabricating projections in the first surface of the substrate, depositing onto the first surface a magnetic material in such a way that the tops of the projections are covered with magnetic material, and depositing filler material atop the substrate so produced. The filler material may then be planarized, for example by chemical-mechanical polishing. In an alternative embodiment magnetic material is deposited on a substrate and portions of it are removed, leaving islands of material. Filler material is then deposited, which may be planarized.

TECHNICAL FIELD

This invention relates generally to magnetic storage media and inparticular to methods for manufacturing media with high density storagecapabilities.

BACKGROUND

It has been believed for some time now that the current magneticrecording media will at some density become unusable on account ofsupraparamagnetism. Supraparamagnetism is a thermal instability of themagnetization in an unpatterned magnetic recording medium which isprojected to occur as the sizes of the magnetic domains approach thesizes of the magnetic metal grains. Because of this belief, there hasbeen a good deal of research into different ways of overcoming thesupraparamagnetic limit by making patterned magnetic recording media.See, e.g., C. A. Ross, “Patterned Magnetic Media,” Annual Rev. Mater.Res. 31:203-35 (2001). Furthermore, patterned media offer less magneticrecording noise at the same recording density point.

In more detail, as we scale continuous media to smaller bit (or magneticdomain) dimensions, we also have to scale grain sizes, because signal tonoise ratio is roughly proportional to the number of grains. At somepoint, those grain sizes become so small, that the thermal energy aloneis sufficient to flip the bit, and the media becomes unstable. Thecritical grain volume V_(g) that determines the onset ofsupraparamagnetic limit is determined by the condition that the storedmagnetic energy K_(u)V_(g) is about 40-60 times larger than the thermalenergy k_(B)T, where K_(u) and k_(B) are the magnetic anisotropy andBoltzmann constant, and T is the temperature. When bit densities arehigh enough that grain sizes in unpatterned media fall below thecritical grain volume, patterned media is preferred since it offers onerelatively large island of magnetic material, acting as a singlemagnetic domain, and therefore has an improved signal to noise ratio. Itis believed that recourse to patterned media may become necessary atrecording densities of very roughly 500 Gb/in² to 1000 Gb/in².

Possible approaches to achieving densities of 500 Gb/in² includeperpendicular recording and thermally assisted writing on highcoercivity media. However, these approaches have not yet beendemonstrated to be viable for data storage densities on the order of 500Gb/in².

Perpendicular recording refers to data recording on a hard disk in whichthe poles of the magnetic bits on the disk are aligned perpendicularlyto the surface of the disk platter. Perpendicular recording can deliverup to 10 times the storage density of longitudinal recording, on thesame recording media. Current hard disk technology with longitudinalrecording has an estimated limit of 100-150 Gb/in² due to thesuperparamagnetic effect. As discussed above, it is estimated that, whenthe bits are of the size required to achieve densities above that limit,the grain size becomes so small that thermal energy alone can flip itsmagnetization direction. This would cause random data corruption whichwould be unacceptable in practice. Perpendicular recording gets aroundthe supraparamagnetic limit by re-aligning the poles of the bitsperpendicularly to the surface of the disk so they can be placed closertogether on the platter, thus increasing storage density by a factor of10.

U.S. Pat. Nos. 6,313,969, 6,420,058, and 6,440,520, for example, teachmethods of making patterned magnetic media.

An important issue with patterned magnetic media is the level ofperfection associated with the planarization of the disk. For example,the read/write head of a data storage device must be able to fly overthe face of a disk rotating at speeds ranging from 3600 up to 15000 rpm,to read or write on concentric data tracks disposed on the surface ofthe disk. The spacing between read/write head and disk surface as thehead flies over that surface is measured in nanometers, thus requiringminimal anomalies in the disk surface to assure smooth flying for theread/write head. A preferred approach to minimizing anomalies in themedia used in a data storage device is to planarize the patterned media.

There is consequently a need in the art for a method of making patternedmagnetic recording media which allows good planarization as a part ofthe manufacturing process.

SUMMARY OF THE INVENTION

In one embodiment of the invention, there is provided a method offorming a plurality of regions of magnetic material in a substratehaving a first approximately planar surface. The method comprises thesteps of fabricating projections in the first surface of the substrate,depositing onto the first surface a magnetic material in such a way thatthe tops of the projections are covered with magnetic material, anddepositing filler material atop of the substrate so produced. The fillermaterial may then be planaraized by known techniques.

In an alternative embodiment of the invention, there is provided amethod of forming a plurality of islands of magnetic material atop asubstrate having a first approximately planar surface. The methodcomprises the steps of depositing magnetic material over the firstapproximately planar surface, selectively removing portions of themagnetic material so as to leave islands comprising the material, anddepositing filler material atop the substrate produced in the precedingstep.

FIGURES

FIGS. 1A-1B depict schematically (not to scale) the state of a substrateafter successive processing steps making up a method of the invention.

FIG. 2 depicts schematically (not to scale) the state of a substrateafter successive processing steps making up an alternative method of theinvention.

FIGS. 3A-3B depict schematically (not to scale) the state of a substrateafter successive processing steps making up a further method of theinvention.

FIGS. 4, 5, and 6 depict schematically (not to scale) the state of asubstrate after successive processing steps making up further methodswithin the scope of the invention.

FIG. 7 depicts the shape of the substrate of Example 1 at anintermediate stage of processing, after the deposition of the SiO₂ andbefore the chemical-mechanical polishing.

FIG. 8 is a view of the shape of the substrate of Example 1 at highermagnification than FIG. 7.

FIG. 9 depicts the shape of the substrate of Example 1 afterchemical-mechanical polishing.

FIGS. 10A-10C depict the result of the magnetic material deposition ofExample 2 via a cross-sectional SEM image (FIG. 10A), atomic forcemicroscopy (FIG. 10B), and magnetic force microscopy (FIG. 10C).

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Before describing the present invention in detail, it is to beunderstood that this invention is not limited to specific solvents,materials, or device structures, as such may vary. It is also to beunderstood that the terminology used herein is for the purpose ofdescribing particular embodiments only, and is not intended to belimiting.

As used in this specification and the appended claims, the singularforms “a,” “an,” and “the” include both singular and plural referentsunless the context clearly dictates otherwise. Thus, for example,reference to “a ferromagnetic material” includes a plurality offerromagnetic material as well as a single ferromagnetic material,reference to “a temperature” includes a plurality of temperatures aswell as single temperature, and the like.

The term “substrate” refers to any type of substrate considered suitablefor the manufacture of a magnetic recording medium. The term also refersto the substrate and the materials deposited on it during or after anyof the various stages of treatment through which it goes during theprocess of magnetic recording medium manufacture, for example during orafter the deposition of a magnetic layer.

In describing a substrate comprising multiple layers, reference issometimes made to an “upper” layer, a “top” layer, or a “lower” layer.In general, an “upper” layer refers to one which is deposited after thelayers described as lower. There is no intention to suggest by thisterminology that the deposition must necessarily be done with the“upper” layer lying above the “lower” layer in the ordinary sense ofbeing farther from the center of the earth. Similarly, when one speaksof depositing “atop” a substrate or a layer of a substrate, one meansonly that the deposited material is added to the side of the substrateto which material has previously been added; there is no implicationthat the deposition takes place with the material flowing downward inthe ordinary sense of flowing towards the center of the earth.

“Optional” or “optionally” means that the subsequently describedcircumstance may or may not occur, so that the description includesinstances where the circumstance occurs and instances where it does not.

Relevant information regarding the fabrication processes known to thoseof skill in the art can be found, for example, in Sami Franssila,Introduction to Microfabrication (John Wiley & Sons, 2004).

In one embodiment of the invention, there is provided a method offorming a plurality of regions of magnetic material in a substratehaving a first approximately planar surface. The method comprises thesteps of fabricating projections in the first surface of the substrate,depositing onto the first surface a magnetic material in such a way thatthe tops of the projections are covered with magnetic material, anddepositing filler material atop of the substrate so produced. The fillermaterial may then be planarized by known techniques.

In carrying out this embodiment of the invention, it is preferred that astop material be deposited on top of the substrate after the magneticmaterial has been deposited and before the filler material is deposited.This stop layer may facilitate the use of certain planarizationtechniques such as chemical-mechanical polishing (CMP).

The substrate upon which this embodiment of the invention is practicedconveniently has an upper layer which has been deposited upon the lowerlayer. The upper layer may be, for example, SiN_(x), silicon dioxide, orsilicon, and the lower layer may, for example, be glass, aluminum, orsilicon. The process of formation of the projections in the surface mayconveniently take place in the upper layer. In this way the overallstability and handling of the substrate is provided by the lower layer,while the upper layer can be chosen to be one in which it is simpler tomake projections.

The projections may be made by any process which is convenient, forexample in light of the material of which the approximately planarsurface of the substrate is made. In general, the projections may beformed by removing material in a pattern on the surface to a suitabledepth which leaves the projections standing in relief. For example, itmay be convenient to deposit resist atop the surface, pattern theresist, and use the patterned resist as a mask in reactive ion etching.The patterning of the resist may take place by a method known in theart, such as photolithography or nanoimprinting. Other techniques forproducing the desired pattern on the resist layer include electron beam,projection beam or ion beam lithography, or short wavelengthlithography.

The projections are preferably separate in that they do not physicallytouch each other, at least in the areas close to their tops. Formagnetic recording applications, such physical separation between theprojections may be desired in order to physically separate the magneticmaterial atop each projection from that on adjacent projections. Theprojections may be, for example, in a regular pattern like the redsquares of a checkerboard. The areas of the surface which are not partof the projections may consist of areas which touch and merge. Theprojections are commonly also referred to as posts, pillars, or islands.

The deposition of the magnetic material atop the projections may also bemade by any process which is convenient. It may for example be made byevaporation, chemical vapor deposition, or physical vapor deposition inany of its variants.

The magnetic material may also be of any type which is considered usefulfor the magnetic recording system being designed. For example, it mayconsist of a single layer of a suitable material such as FeN, NiFe, orCoZr. It may also consist of multiple layers of different materials,such as Co and Pt or Ni or Pd. A preferred magnetic material is a set oflayers of Ta/Pd/(Co/Pd)_(n)/Pd, for example 1 nm Ta/3 nm Pd/(0.32 nmCo/0.85 nm A Pd)₈/1.5 nm Pd.

If a stop layer is used, it may also be of a suitable material which forexample causes a discernible slowing down of the planarization process.It may be, for example, diamond-like carbon (DLC) or TiN.

Diamond-like carbon (DLC) refers to many new forms of carbon which haveboth graphitic and diamond-like characteristics. DLC has many possiblematerial properties as it becomes more diamond-like and crystalline. Itsdensity is generally between graphite and diamond (2.2-3.5 grams/cubiccentimeter). The optical properties are normally diamond-like in indexof refraction but a high extinction coefficient makes the material dark.DLC is being used in the semiconductor industry and as a wear resistantcoating for disks used in hard disk drives.

The filler layer may also be of a suitable material which may be morerapidly removed in planarization than the stop layer. This filler layermay be, for example, silicon dioxide, alumina, a metallic nitride.

The step of planarizing may also be carried out by any suitable method.Chemical-mechanical polishing is expected to be quite satisfactory inhard disk applications, particularly if a stop layer is employed.Alternative methods may include planarization with a directionalhigh-incidence-angle broad ion beam, or application of spin-coated ordip-coated polymer that may be planarized by the type of disk burnishingprocess already typically utilized in the disk manufacturing process.Regarding disk burnishing see, for example, U.S. Pat. No. 7,094,129assigned to the assignee of the present application and the referencescited in that patent.

Typically, for hard disk drive magnetic recording media, one would wishto apply a lubricant after the step of planarization. Lubricants fordisk drives are well known and there are a number of lubricants whichcan be used.

FIGS. 1A-1B depict a particular method within the embodiment beingdiscussed here. In the top line of FIG. 1A, we see the startingsubstrate which consists of a layer of SiN_(x) 10 atop a layer of glass12. In the following line, we see the result of deposition a layer ofresist 14 atop the starting substrate. In the following line, the resisthas been nanoimprinted so that it has a pattern. In the following line,the patterned resist has been used as a mask in order to dry etch theSiN_(x) layer, producing indentations such as 16 and thus leaving in thearea where the indentations are not present a series of posts.

In the following line of FIG. 1A, the resist has been removed. In thebottommost line of FIG. 1A, we see the result of deposing a magneticmaterial 18, for example a Ta/(Co/Pd)_(n)/Pd multilayer, atop thesubstrate following removal of the resist. The depth of the etch intothe disk is preferably sufficient to assure adequate magnetic decouplingof the magnetic materials deposited on the tops of the posts such as 20from those materials deposited in the valleys between and surroundingthe posts. Typical depths for the etch into the disk are 40-50 nm. It isin general desired that there be a density of posts corresponding to thebit density to be achieved, for example, 100 billion posts per squareinch, 200 billion posts per square inch, 300 billion posts per squareinch, 400 billion posts per square inch, 500 billion posts per squareinch, 700 billion posts per square inch, or 1000 billion posts persquare inch. A density of 500 billion posts per square inch would mean aseparation between posts of approximately 35 nm.

In the top line of FIG. 1B, we see the following step of the exemplaryprocess, which deposits a DLC stop layer 22 above the layers depositedpreviously. Typical thicknesses for the DLC layer are 2-10 nm. Thefollowing line shows the result of depositing a filler 24, which may besilicon dioxide, alumina, or another suitable material. Finally, thebottom line of FIG. 1B depicts the result of subjecting the substratewith the layers so far deposited to chemical-mechanical polishing (CMP).

In an alternative embodiment of the invention, there is provided amethod of forming a plurality of islands of magnetic material atop asubstrate having a first approximately planar surface. The methodcomprises the steps of depositing magnetic material over the firstapproximately planar surface, selectively removing portions of themagnetic material so as to leave islands comprising the material, anddepositing filler material atop the substrate produced in the precedingstep. The filler material may then be planarized by known techniques.

The step of selectively removing portions of the magnetic material maybe assisted by the use of a mask. In a preferred embodiment, the mask isformed by depositing a mask material, depositing resist atop the maskmaterial, patterning the resist, transferring the resist pattern to themask material, and removing the remaining resist. The mask material ispreferably DLC with thickness between 2-10 nm. The patterning of theresist may occur by any method, for example those listed above, withnanoimprinting being particularly preferred. The transfer of the resistpattern to the mask material may employ any suitable method, such asreactive ion etching.

Once a mask is in place, the selective removal of portions of themagnetic material may occur by any suitable method, for example ionmilling. It is commonly desired that this selective removal result inleaving pillars of magnetic material on the substrate. Each of thesepillars may be left covered with the remaining mask material at the top.Above this, filler material may be deposited covering the pillars andthe spaces between them.

Once the filler material has been deposited, it may be planarized by anysuitable method such as chemical-mechanical polishing (CMP). Where themask material is a suitable stop material for the planarization, e.g.,as where DLC mask material is used together with CMP, leaving the maskmaterial on top of the pillars is helpful to simplify processing.

The magnetic materials usable in this embodiment will generally be thesame as those set out above in connection with earlier embodiments.

In line with the discussion above, in disk drive applications the sizeand spacing of the pillars formed in this process will be as appropriatefor the density of recording sought to be achieved. Thus for example ifthe density is 500 billion bits per square inch, one may calculate that500 billion˜707107² so that a linear density of 707107 pillars per inchwill give 500 billion bits per square inch. In more familiar units,707107 pillars per inch means that the pillars should be spacedapproximately 35 nm apart (0.0254 meters/inch divided by 707107 pillarsper inch). In embodiments that have pillars made primarily of magneticmaterial, there is a desire to have these pillars be as tall as thefabrication technology can usefully make them, e.g., an aspect ratio of2:1, 3:1, 4:1 or 5:1 (height/diameter).

FIG. 2 depicts a particular embodiment of the invention. In the firstline, one sees that a magnetic material 30 has been deposited on asuitable substrate material 32 such as glass or silicon. A mask material34 such as DLC is then deposited on top of the magnetic material. Aresist material 36 is then deposited on the mask material and patternedby, for example, nanoimprinting. In the next line, we see that thepattern of the resist has been transferred to the mask material and thento the underlying magnetic material, via processes such as reactive ionetching or ion milling. The resist is then removed as seen in the nextline, leaving pillars such as 38. The filler material 40 (e.g., alumina)is then deposited, and is then planarized as shown in the bottommostline of FIG. 2.

FIGS. 3A and 3B depict a different embodiment of the invention. As inthe embodiment of FIG. 2, we start in the top line of FIG. 3A withmagnetic material 50 deposited on a suitable substrate material 52. Themask material 54, which may be for example 30-50 nm thick polyimide, isdeposited atop the magnetic material. Patterned resist 56 is depositedatop the mask material, the patterning being accomplished by anysuitable means. A suitable metal 58 (e.g., Ge, Ta, Ti) is thendeposited, and resist is removed by means of a lift-off procedure. Thisleaves a metallic mask atop the mask material. Using that metallic mask,the mask material is patterned, for example by a suitable etchingprocess, leaving the substrate in the state depicted at the bottom ofFIG. 3A.

The manufacturing process continues, as shown in the top line of FIG.3B, by transferring the pattern now present in the metal and maskmaterial to the magnetic material, thus forming pillars such as 60. Thetransfer may occur, for example, by ion milling. The substrate with thepillars is then covered with a stop material 62, with the depositionbeing carried out so that the amount of stop material between thepillars matches the height of the magnetic material. At that point,planarization is carried out, leaving pillars of magnetic materialsurrounded by stop material, as depicted in the bottom row of FIG. 3B.

FIG. 4 depicts another embodiment of the invention. As in FIG. 2A,magnetic material 70 is deposited upon a suitable substrate 72, a maskmaterial 74 is deposited on top of the magnetic material, andphotoresist 76 is deposited atop the mask material and patterned bynanoimprinting. The resist pattern is transferred to the mask materialand then to the magnetic material. At that point, filler material 80 andthen additional mask material 78 are deposited. The deposition is againarranged so that the thickness of the deposited material approximatelyequals that of the magnetic material, and thus the mask material againforms an approximately continuous sheet atop the magnetic and fillermaterial. The resist and materials atop the resist are then removed,e.g., by CMP-assisted lift-off, leaving a surface which is approximatelyplanar and can be planarized and lubricated with a lubricant 82, asshown in the bottom line of FIG. 4.

In FIG. 5 a variant of the process of FIG. 4 is depicted. Following thetransfer of the resist pattern to the magnetic material we have thesituation shown in the top line of FIG. 4, with pillars such as 90containing magnetic material, mask material, and resist. At that point,unlike in FIG. 4, the remaining resist is removed, e.g., chemically. Theprocess then proceeds as in FIG. 4, with deposition of filler materialand mask material to a depth matching that of the magnetic material andthen removal of the filler and mask material lying above the originallevel of the mask material, e.g., via CMP-assisted lift-off.Planarization and lubrication may follow.

In FIG. 6 a variant combining the processes of FIGS. 1A-1B and FIG. 5 isshown. The top line shows the result of the process steps of FIG. 1A,which result in indentations 100 containing magnetic material topped bya stop material, and pillars 102 with magnetic material and stopmaterial atop a different material, so that the magnetic material indepressions 100 and pillars 102 is spatially separated. Now, instead ofdepositing just filler as in FIG. 1B, we deposit both filler 106 andadditional stop material 104. Following the removal of the material atopthe pillars by CMP-assisted lift-off, there remains a continuous layer108 of stop material, as in FIG. 5. Further processing may occur as inFIG. 5.

In reading FIGS. 1A-6 the person of skill in the art will understandthat the representation of the results of deposition is schematic. Whilein general it is desired that there be no step coverage, so that allparticles being deposited would have a path which is straight down ifthe substrate is horizontal, it will be recognized that this may not beachievable in practical methods of deposition. Alternatively, forexample with respect to the magnetic material, if it is applied inlayers, layers of one material may be applied pointing straight down,and layers of the other material at a raking angle, so that thesidewalls and bottoms are mostly composed of one material and createlittle magnetic coupling between the multilayer material at the tops ofdifferent pillars.

As has been indicated above, a preferred use of the methods of theinvention is to manufacture patterned magnetic recording media suitablefor use as disks in hard disk drives. The scope of the invention alsoencompasses hard disk drives which contain patterned magnetic media.Such a disk drive comprises one or more data storage media or disks onwhich data is stored in digital form on magnetic bits disposed on thedisk for receiving the data. The disks rotate at speeds of 3600 rpm,7200 rpm, or higher. Magnetic bits are disposed in concentric ringscircling the center of the disk, each bit consisting of a region ofmagnetic material spatially separated from other such regions. The harddisk drive has the ability to write and overwrite data to bits, as wellas read the data stored on the bits. This is generally accomplished bymeans of one or more magnetic heads which are mounted on sliders, inturn mounted on arms with appropriate suspensions, acting under thecontrol of an electronic controller. The arms generally move in such away that the heads can be positioned over any desired radial position ofeach disk. When the disk is in operation, the heads fly over the surfaceof each disk, being kept apart from the surface by air bearings whichform part of the sliders. The heads create a suitable magnetic field forwriting which causes a bit to shift its state to align itself with thefield, while they sense the magnetic fields at each point on the surfaceof the disk for reading.

It is to be understood that while the invention has been described inconjunction with the preferred specific embodiments thereof, theforegoing description is intended to illustrate and not limit the scopeof the invention. Other aspects, advantages, and modifications withinthe scope of the invention will be apparent to those skilled in the artto which the invention pertains.

All patents, patent applications, and publications mentioned herein arehereby incorporated by reference in their entireties. However, where apatent, patent application, or publication containing expressdefinitions is incorporated by reference, those express definitionsshould be understood to apply to the incorporated patent, patentapplication, or publication in which they are found, and not to theremainder of the text of this application, in particular the claims ofthis application.

EXAMPLE 1

A silicon substrate was prepared by depositing 200 nm silicon dioxideatop it. Resist was placed on the silicon dioxide and then pattered bothoptically and with an electron beam. The silicon dioxide was etched andthe resist removed. The optical patterning left hollow cylindricalpillars and rows of synchronization marks. The electron beam patterningleft square areas of pillars which were 100 μm by 100 μm and disposed1000 μm apart from each other. Within each square area of pillars, theelectron beam patterning left pillars at a particular density, chosenfrom among 101 billion per inch², 213 billion per inch², and 318 billionper inch². Following this patterning of the SiO₂, 30 nm of NiFe, 5 nm ofDLC, and 250 nm of SiO₂ were deposited.

The result of this patterning is shown in FIGS. 7 and 8, which are basedon measurements made by atomic force microscopy. In FIG. 7, one can seethe hollow cylindrical pillars made by optical lithography at the bottomleft. In the upper right half of the figure one can see first thesynchronization marks also made by optical lithography, and then to theright of them a part of a square area of pillars made by electron beampatterning. In FIG. 8, one sees in greater detail the pillars in thesquare area made by electron beam patterning. The optical features weremeasured to be 41 nm above the field SiO₂ while the electron beampillars were 33 nm above that.

At this point chemical-mechanical polishing was carried out. The CMPtool was a tabletop polisher with a 15 inch pad. An IC1000 pad with SubaIV subpad was employed together with a silica slurry. An increase in thecoefficient of friction, attributed to the DCL stop layer, was used asan indicator to stop the polishing.

The result of the CMP is depicted in FIG. 8, also based on atomic forcemicroscopy. It may be seen that the electron beam pillars were smootheddown by the CMP to a height of about 3 nm.

EXAMPLE 2

The fabrication process started with a glass disk coated with 40 nm ofSilicon Nitride (SiNx). The disk was coated with 85 nm of PMMA electronbeam resist. After electron beam lithography exposure of the patterns,resist was developed and the sample coated with 20 nm of chromium. UsingNMP solvent, Cr metal was lifted off and a pattern of Cr dots wascreated. The Cr metal pattern was transferred into a SiNx film usingreactive ion etching employing CF₄ gas chemistry. After the SiNx pillarpattern was created, magnetic media was sputter-deposited on thepatterned disk substrate. A cross-sectional SEM image (FIG. 10A) of thepatterned disk substrate demonstrates that the amount of materialdeposited on the sidewalls may be controlled. The topographic AFM image(FIG. 10B) and magnetic force microscopy (MFM) image (FIG. 10C) of apatterned media disk at moderate bit areal density of 100 Gb/in²demonstrate that individual islands are successfully magneticallyisolated, with two magnetic states clearly visible. That the islands aremagnetically isolated is confirmed by observing a random pattern ofmagnetically oriented bits, instead of large regions of many bitsoriented in the same direction.

1. A method of forming a plurality of regions of magnetic material in asubstrate having a first approximately planar surface, comprising:fabricating a plurality of projections in the first surface of thesubstrate such that each projection comprises a top; depositing, ontothe first surface of the substrate after fabrication of the projections,a magnetic material in such a way that the tops of the projections arecovered with the magnetic material and the magnetic material on the topof each projection is magnetically decoupled from the magnetic materialon the tops of the other projections; depositing stop material atop thesubstrate produced in step b), the stop material comprising a materialchosen from the group consisting of diamond-like carbon, TaN, TiN, andtantalum; and depositing filler material above the stop materialdeposited atop the substrate.
 2. The method of claim 1, wherein thefabricating comprises: depositing a the mask material atop the firstsurface of the substrate, depositing resist atop the mask material,patterning the resist, transferring the pattern in the resist to themask material, and removing the mask material.
 3. The method of claim 2,wherein the mask material is chosen from the group consisting of siliconnitride and silicon dioxide.
 4. The method of claim 1, furthercomprising depositing a layer of further material atop the fillermaterial.
 5. The method of claim 1, wherein the magnetic materialcomprises multiple layers.
 6. The method of claim 5, wherein themagnetic material comprises Ta, (CoIPd), and Pd layers.
 7. The method ofclaim 1, further comprising planarizing the filler material.
 8. Themethod of claim 7, wherein the planarizing of the filler materialcomprises chemical-mechanical polishing (CMP).
 9. The method of claim 2,wherein the mask material is removed using reactive ion etching.
 10. Themethod of claim 7, further comprising depositing a mask atop themagnetic material such that the mask serves as a stop material for theplanarizing.
 11. The method of claim 1, wherein the filler material isdeposited to a thickness approximately equal to the tops of theprojections covered with the magnetic material.
 12. The method of claim1, wherein the projections are spaced at a density of at least about 300billion per square inch.
 13. A method of forming a plurality of regionsof magnetic material in a substrate having a first approximately planarsurface, comprising: fabricating projections in the first surface of thesubstrate such that each projection comprises a top; depositing, overthe first surface of the substrate after fabrication of the projections,a magnetic material in such a way that the tops of the projections arecovered with the magnetic material and the magnetic material on the topof each projection is magnetically decoupled from the magnetic materialon the tops of the other projections; depositing a mask atop themagnetic material; depositing filler material above the substrate;depositing a further layer of material atop the filler material, thefurther layer of material being deposited to approximately the samethickness as the mask; and planarizing the filler material by applyingspin-coated or dip-coated polymer and planarization of the appliedpolymer by disk burnishing.
 14. The method of claim 7, wherein theplanarizing of the filler material comprises planarization with adirectional high-incidence-angle broad ion beam.
 15. The method of claim7, wherein the planarizing of the filler material comprises applicationof spin-coated or dip-coated polymer and planarization of the appliedpolymer by disk burnishing.
 16. The method of claim 13, wherein theprojections are spaced at a density of at least about 300 billion persquare inch.
 17. The method of claim 9, further comprising patterningthe mask material using a resist material deposited atop the maskmaterial.
 18. A method of forming a plurality of regions of magneticmaterial in a substrate having a first approximately planar surface,comprising: fabricating a plurality of projections in the first surfaceof the substrate such that each projection comprises a top, thefabricating comprising: depositing a mask material atop the firstsurface of the substrate, depositing resist atop the mask material,patterning the resist, transferring the pattern in the resist to themask material, and a removing the mask material; depositing, onto thefirst surface of the substrate after fabrication of the projections, amagnetic material in such a way that the tops of the projections arecovered with the magnetic material and the magnetic material on the topof each projection is magnetically decoupled from the magnetic materialon the tops of the other projections; depositing filler material abovethe substrate; and removing the resist via lift-off.
 19. A method offorming a plurality of regions of magnetic material in a substratehaving a first approximately planar surface, comprising: fabricatingprojections in the first surface of the substrate such that eachprojection comprises a top; depositing, over the first surface of thesubstrate after fabrication of the projections, a magnetic material insuch a way that the tops of the projections are covered with themagnetic material and the magnetic material on the top of eachprojection is magnetically decoupled from the magnetic material on thetops of the other projections; depositing a mask atop the magneticmaterial, the mask having a thickness, the mask comprising a firstmaterial; depositing filler material above the substrate; depositing afurther layer of material atop the filler material, the further layer ofmaterial comprising the first material; and planarizing the fillermaterial by applying spin-coated or dip-coated polymer and planarizationof the applied polymer by disk burnishing.